This project is a neuroanatomical investigation of the efferent projections of the brainstem reticular formation. Studies of retrograde degeneration of cell bodies in the reticular formation after diencephalic lesions and retrograde transport of horseradish peroxidase injected into the diencephalon are used to determine the source of reticular efferents to the thalamus and subthalamus. Autoradiographic studies using orthograde transport of tritiated leucine, along with orthograde degeneration studies, are used to determine the precise diencephalic areas of termination of reticular projections. Autoradiographic and orthograde degeneration studies are also being used to investigate projections of the diencephalic areas which receive major afferents from the reticular formation. These studies will provide the basis for a better understanding of the role of the reticular formation in influencing the function of the forebrain. BIBLIOGRAPHIC REFERENCES: Robertson, R. T., K. S. Mayers, T. J. Teyler, L. A. Bettinger, H. Birch, J. L. Davis, D. S. Phillips and R. F. Thompson. Unit activity in posterior association cortex of cats. J. Neurophysiol., 1975, 38, 780-794. Mayers, K. S., R. T. Robertson, T. J. Teyler and R. F. Thompson. Response properties of single units in an association area of the kitten neocortex. Physiol. Behav., 1976, in press.